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TMS320F28027F: Unable to start motor at low temperature

HY yang
Expert 1980 points
Part Number: TMS320F28027F


This is a motor driven product, currently encountering situations where a room temperature motor can start normally, but the lower the temperature, the more difficult it is to start.

When starting at a standstill, the software has enabled the forced angle gMotorVars.Flag_ EnableForceAngle=1. The test found that the frequency of the current waveform in the first electrical cycle increased significantly during startup at -20 ℃, resulting in the inability to start. May I ask what may be the reason for this situation? We have not improved the filtering by increasing or decreasing the sampling of phase voltage and phase current in terms of hardware.

2. I will add gMotorVars.Flag_ The enableForceAngle is set to 0, and the forced angle is not turned on when stationary. Starting at -20 ℃ is normal. What may be the reason for this?

3. In 2018, TI's FAE engineers asked us to integrate gMotorVars.Flag_ The enableForceAngle setting was set to 1 to deal with the situation where the reverse 0 to 250 revolutions cannot be started without opening the forced angle. Could you please help analyze if there are any issues with canceling the forced angle (gMotorVars. Flag_enableForceAngle set to 0)?

The waveform of motor phase current during normal startup is shown in the following figure:

Under low temperature conditions, the waveform of motor phase current during abnormal startup is shown in the following figure:

  • +1
    TI__Mastermind 45606 points

    Hi HY,

    HY yang said:
    currently encountering situations where a room temperature motor can start normally, but the lower the temperature, the more difficult it is to start.

    Stator resistance can vary over temperature, this may be the cause of this behaviour.You can try using the Rs Re-calibration function at start-up and see if it offers any improvement. The routine can also be run “On-the-fly” to track stator resistance changes in real time.

    Best,

    Kevin

  • 0 in reply to Kevin Allen18
    Expert 1980 points

    During our test, the motor was placed outside the low-temperature chamber, and only the controller was in the low-temperature chamber, so it was excluded that the motor parameters were affected by temperature. It was normal to follow the output waveform test of the main control chip to PIM. However, we could not judge the changing trend of PWM duty ratio, because it was a closed-loop. The sampling of phase current and terminal voltage will affect the starting waveform.